Ferroprussiate photoreproduction



Patented Feb. 6, 19 40 UNITED STATES PATENT OFFICE maaoraussm'm rno'roanrnonuo'rron No Drawing. Application November 30, 1937,

Serial No. 177,321. In Great Britain December 8 Claims.

and a controlled intensity of blue effected in the.

development and not requiring subsequent treatment to effect their ends.

by sensitising the paper with solution containing a salt' of iron in the ferric state, preferably a double salt with an alkali of an organic acid; a ferro-cyanide with or without a ferri-cyanide; a suitable buffer salt in neutral or alkaline condition: a fixing agent or agents being applied to the sensitised coating in whole or in part before or after exposure to light, such fixing agents being capable of rendering insolublethe ferrocyanide and the ferri-cyanide, when in contact v with water but being chemically separated from the cyanides ifapplied before exposure to light; intensifying or stabilising agents may also be applied under the same conditions as the fixing agents, the paper being developed by water or aqueous solution contact as distinct from washmg.

According to one mannerof carrying out the invention a paper of the kind known in the art to be suitable forprinting papers "of this kind is coated with a sensitising solution containing a salt'of iron in the ferric state, and preferably 40 a double salt with an alkali salt of an organic acid. such as ferric ammonium oxalate, and a suitable ferro-cyanide, such as potassium ferrocyanide or a mixture of potassium ferro-cyanide and a ferri-cyanide such as a potassium ferri-cyanide, or if desired the ferro-cyanide may be used alone. The function of the vterm-cyanide is to give'higher printing speeds, and also to allow a wider range of exposure. The solution also contains ab'uifer salt, which may preferably be an alkaline oxalate, citrate or tartrate; acids 5 must not be present. 'Photosensitive papers of the above type may be termed ferroprussiate papers.

Agents for fixing, stabilising or intensifying theprint to be made on the paper are used and agents for all these purposes, or for any ofthese According to this invention light sensitive printing paper of the kind referred to is made purposes, may be applied or added in whole or in part 'to the paper before its exposure to light and subsequent development by contact with water or by an aqueous solution. If however, any of these agents are applied before the ex- & posure of the paper precautions must be taken to prevent any reaction between them and the sensitised surface beforesuch exposure to light takes place, thus ensuring that such agents can only enter into their desired chemical reaction W when water or an aqueous developer is applied If by mischance the .paper should come into contact with water or aqueous solution or should become wet before exposure it will be spoiled; except by accidents or carelessness such contact does not occur.

In some instances the whole of one or more of such agents which may be required may be applied to the paper before exposure to light, and in'other instances part only may be applied, the required balance being applied after exposure, or in other instances the whole of some, and part of the other agents may be applied before or after exposure.

Where the agents are not on the paper before exposure precautions must be taken to ensure the complete fixing of the print according to the thickness and type of the paper such as by treating the paper more than once with the developing solution either on the front or back or both,

,such treatment being however distinct from;

washing,

Agents which can be used for fixing or forming the insoluble salts with the ferroor ferri-cyanides, but which do not constitute a complete list and which may not all beequally effective in everyinstance are metallo organic saltssuch as zinc, nickel, cobalt saltsor aliphatic or aromatic acids, such as zincsalts of naphthalene sulphonic acids, or zinc salts of phenol sulphonic acids or certain metallic salts of the sulphuric acid esters of high fatty alcohols or the corresponding salts of the other metals named or of other metals which will form insoluble or non-reactive ferroor ferri-cyanides. v There may also be used salts of inorganic acids of similar metals soluble in water e. g. zinc, nickel, cobalt sulphates or insoluble or slightly soluble salts, e. g. the oxides, carbonates or similar insoluble salts of metals which will form ide, chloramines, hypochlorites, salts of paradichlorosulphonamino benzoic acid. Certain oxidising agents may also have the property of forming insoluble or non-reactive salts with the ferroor ferri-cyanides as well as acting as intensifying and stabilising agents to the background e g. metallic peroxides, persulphates, chromates and double salts with the alkali persulphates or hypochlorites.

A wetting agent may be used if desired and to counteract or destroy its effect at any convenient stage a metallic salt may be used, such salt being one that will form an insoluble salt with the wetting agent e. g. barium salt.

Papers made according to this invention are easily developed by contact with a film of water or a developer in aqueous solution.

While papers according to this invention have been referred to as blue prints they are usually, though not necessarily, deep blue and clear white prints; cream or yellow lines can be made; the term blue print is however used to distinguish this branch of the art from the production of diazo-type" papers. v

The invention may be carried out in various ways of which the following are examples.

ExAMrLr: I

A suitable paper is coated with a solution of the following composition:

Part A.-To a volume of 2,000 ccs.

50% solution ferric ammonium oxalate ccs 800 Borax gms 50 Part B.To a volume of 2,000 ccs.

% solution potassium ferro-cyanide.. ccs 700 solution potassium oxalate (neutral) ccs 500 solution potassium ferri-cyanide ccs 100 20% solution gum arabic ccs 100 Cane sugar gms 400 Part A is added to Part 13. Final volume 4,000 ccs.

The coated paper is dried and after exposure to light under a design is developed by the application of a thin film of a solution of the following composition:

Zinc sulphate crystals i gms 50 Magnesium sulphate crystals gms 50 Mono-sodium-ortho-phosphate crystals gms 50 Ammonium persulphate gms 15 Wetting agent per cent 1 to 2 Water to a final volume of 500 cos.

In the following example the agent used to form the insoluble ferroand ferri-cyanides is applied to the surface of the paper in the form of a fine dry powder before exposure to light.

A suitable paper is coated with the light sensitive solution described in Example I and dried,

the dry sensitize surface is then dusted with a fine dry powder of the following composition:

Excess of powder is removed by suitable means 'such as a brush rotating at high speed. Papers so obtained after exposure to light under a design are developed by the application of a thin film ofasolution of the following composition.

Magnesium sulphate gms 50 Mono-sodium-ortho-phosphategms 75 Wetting agent per cent 1 to 2 Prints in bright yellow lines which bleach to cream or white on exposure to light, on a stable blue background are obtained.

Part or whole of the wetting agents may be included in the dry powder.

Part or whole of one or the other agents used in the developer may be applied in the dry powder, and when all are appliedin powder form, the print is developedby contact with a film of water.

The powdered composition may be applied to the back or unsensitised side if very thin e. g. 30 gram papers are used, or if a thick, absorbent paper is used it is treated in such a manner as to ensure that the necessary chemical reaction will take place.

When powdered agents are to be applied to the surface of the paper, it has been found that the best results are obtained with amatt or semi-matt paper. Smooth papers generally do not give the best results.

Exmu: III

In the following example the agent used to form the insoluble term-cyanide or ferri-cyanide is applied before exposure to light in non-aqueous solution.

A suitable paper is coated with the light sensitive solution described in Example I and dried. The dry paper is then coated on the sensitive side, or if the paper is absorbent on the reverse side with a 10% alcoholic solution of a zinc salt of naphthalene sulphonic or disulphonic .acid, and

the alcohol is removed by drying in a current of warm air. Paper so prepared, after exposure to light under a design is developed by the application of a thin film of a solution of the following composition:

Magnesium sulphate gms Mono-sodium-ortho-phosphategms '75 Ammonium persulphate gms 20 Wetting agent per cent 1 to 2 Water to a final volume of 500 ccs.

Prints with white lines on a stable bright blue back round are obtained.

Salts of other metals such as manganese, nickel with inorganic or organic acids if soluble in a non-aqueous solvent may be used in place oi zinc but may not be equally effective in every case.

The non-aqueous solution may, if desired, contain the whole or a portion of the wetting agent and/or bufi'er agents.

Exmu IV In the following example the agent used to form the insoluble ferroand ferri-cyanide is applied before or after sensitising on the back of the paper. Colloids may be used to prevent penetration of a thin paper, or wetting agents may be used to assist penetration of thick or hard surface paper. Contact of the reacting agents after exposure under a design is made by penetration of the paper, and a wetting agent may be used to assist this.

A suitable paper is coated with the light sensitive solution described in Example I and dried. The reverse side is then coated with a solution of the following composition:

. Grams Zinc sulphate 200 Mono-sodium-ortho-phosphate 200' Magnesium sulphate 200 Dextrine 200 made up to 1000 ccs. water and is again dried.

After exposure to light under a design the print is developed by the application of a film of developer, preferably applied to the sensitive side,

of the following composition.

Ammonium persulphate gms Wetting agent (preferably volatile) per cent" 2 to 3 While as herein described the oxidising agent may also be a stabilising agent or line fixing agent, the oxidising agent does not necessarily perform the fimction of a stabilising agent, and a separate stabilising agent may be used instead of. or in addition to, the oxidising agent.

Suitable stabilising agents are buffer salts e. g. the acid or neutral phosphates of the alkali metals or ammonia, orsalts of organic acids such as phthalic, benzoic, or their equivalents, or calcium or magnesium salts e. g. calcium chloride or magnesium sulphate.

What I claim as my invention and desire to secure by Letters Patent is:

1. A light sensitive printing paper having a sensitized coating formed of a solution containing a salt of iron in the ferric state, a ierro-cyanide, a suitable bufler salt, a fixing agent comprising zinc salts of aliphatic acids applied to the sensidl tized coating and capable of rendering insoluble IO development by contactwith water as distinct from washing.

2. A developer for solution in water to fix the unreacted color forming components of a terroof ferroprussiate printing papers which developer comprises the combination of a soluble magnesium salt and the soluble salt of a metal selected from the group consisting of zinc, nickel and cobalt which salts when applied to an exposed ferroprussiate light sensitive layer act in combination to stabilize the blue background against the action of actinic light.

4. A developer for the semi-dry development of ferropiussiate printing papers which developer comprises the combination of a soluble magnesium salt and the soluble salt of a metal which reacts to form insoluble compounds with the iron-cyanogen radicals, which salts when applied to an exposed ferroprussiate light sensitive layer act in combination to stabilize the blue background against the action of actinic light.

5. A developer for solution in water to fix the unreacted color forming components of a ferroprussiate light sensitive layer, stabilize and intensity the color forming components, comprising an oxidizing agent, zinc sulfate, magnesium sulfate and mono-sodium-ortho-phosphate.

6. The process for the semi-dry development of ierroprussiate papers comprising separately fixing the iron ion which has not reacted to form a compound which will be blue, and the ironcyanogen radicals which have not reacted to form a compound which will be blue, which process includes separately applying a metal salt for insolubilizing the iron-cyanogen radicals and a phosphate for insolubilizing the iron ion.

l. The method for stabilizing the blue background of a ferroprussiate print which is fixed by a metal salt comprising applying a solution of a magnesium salt thereto which is retained on the print.

8. A developer for solution in water to fix the unreacted color forming components of a ferroprussiate light sensitive layer; stabilize and intensity the color forming components, comprising a metallo organic salt the metal of which forms insoluble iron-cyanogen compounds, a

, phosphate, an oxidizing agent for iron-cyanogen compounds and a magnesium salt.

JOHN HOLDEN. 

